The use of enzymes for cleaning and removing organic debris (e.g. protein, lipids, etc.) from contact lenses is well known in the art. Common classes of such enzymes include proteases and lipases. Specific examples of enzyme cleaners are available from Bausch & Lomb, e.g. ReNu.RTM. Effervescent Enzymatic Cleaner for soft contact lenses. This cleaner comprises a tablet containing a proteolytic enzyme (subtilisin), polyethylene glycol, sodium carbonate, sodium chloride and tartaric acid. One cleaning regime comprises dissolving the tablet in ReNu.RTM. Multi-Purpose Solution or a sterile saline solution in a vial and soaking a soft contact lens in the solution for at least fifteen minutes. Other enzyme cleaners are also commonly used. For example, liquid enzymatic cleaners have been widely available in Japan for cleaning RGP and hard contact lenses.
Enzymes must be thoroughly rinsed from contact lenses after cleaning and before insertion as the enzymes can cause discomfort if applied to the eye. Unfortunately, enzymes can be difficult to remove from many contact lenses. For example, hydrogel lenses are porous and include a large amount of bound water. Enzymes readily penetrate the pores of these lenses and can associate with the bound water therein, making enzyme removal difficult. With respect to RGP lenses, these lenses commonly have an anionic surface which can attract enzymes and can make enzyme removal difficult. If not removed from the lens after cleaning, enzymes can subsequently be released from the lens and into the eye causing stinging and irritation.
Although enzyme cleaners are effective in removing deposits and debris from contact lenses, their continued association with lenses after cleaning and rinsing causes eye irritation and discomfort. It is desired to provide enzyme cleaners that are more easily removed from a lens following cleaning.